Piping and Instrumentation Diagrams (P&ID) are schemes of pipelines, equipment, instrumentation, control systems, from a process system found in Oil Refinery, Chemical Plant, Paper Mill, Cement Plant, etc.

The symbols contained in P & ID represent equipment such as actuators, sensors and controllers. Process tools such as valves (valves), instruments, and pipelines are identified by code. The codes are based on the size, type of fluid being drained, type of pipe connection (such as using Bolt or Flang), and the status of the Valve status (Normally Close or Normally Open).

How to read a P&ID?

The Instrumentation codes listed in P & ID are as follows, the first letter identifies the parameters that are controlled, the letters then identify the type of control device

Based on the example of the P & ID diagram above, FT101, the first letter F has the meaning of the code (based on the ISA code), namely Flow.

The second letter T has the meaning Transmitter, code FT101 can be interpreted as Flow Transmitter, Circles indicate FT101 mounted (mounted) in the Field Area, which is connected by electric signal (dashed line).

In FIC101, meaning (Flow Indicator Controller), the symbol in the form of a box and circle shows FIC101, located in Shared Control / Shared Displays and can be accessed by the operator.

Process and Instrumentation Symbols – Instruments

The process flow diagram uses symbols and circles to represent each instrument and how they are interconnected in the process.

Process and Instrumentation Symbols – Equipments:

Pumps and tanks come in a variety of designs and shapes.

Process and Instrumentation Symbols – Valves:

Process and Instrumentation Symbols – Piping Lines:

Process flow diagrams use special pipe lines to represent how signals are transmitted between equipment. These symbols are used to identify how the instruments in the process connect to each other. And what kind of signal is being used. (electrical, pneumatic, data, etc.)

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A standard set of symbols is used by the process engineers when designing the Piping and Instrumentation diagrams. The first thing to do when reading P&ID is do get to know the symbol's legend.

Like other specialized diagrams, P&IDs are built up of standard shapes and symbols. There is a huge variety of symbols, depending on industry and manufacturer. Most industries have standardized their symbol representation according to the ISA Standard S5.1 Instrumentation Symbol Specification and use them to design: P&IDs, Flow Diagrams, Logic Plans.

The shapes in the legend are representative of the functional relationship between piping, instrumentation, and system equipment units.

They can be broken to some main groups:
- general instrument or function symbols
- instrument line symbols
- primary elements
- valves
- pumps
- compressors
- vessels
- heat exchangers

On Figure 1 is show a basic example of representing the physical equipment on the in the P&ID.

Figure 1.

General instrument or function symbols

Instrument Line symbols

Primary elements

Valves

Pumps

Centrifugal pumps

Positive displacement pumps

Compressors

Centrifugal compressors

PD Compressors

Heat Exchangers

Filters

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